OBJECTIVE: To study the biochemical mechanism of in vitro transformation in variants subcloned from Balb 3T3 for the purpose of understanding their variabilities in response to chemical carcinogens. APPROACH: (1) Study the metabolic activation of Benzo(g) pyrene (BP) in variants by measuring their induced aryl hydrocarbon, hydroxylase activities; (2) use high-pressure liquid chromatography (HPLC) to analyze metabolites; (3) variants were treated with BP, and their DNA was isolated to compare the amounts of carcinogen bound to DNA; (4) Isolate and identify carcinogen - nucleoside adolucts (5) measure the excision repair in variants.